1. Field of the Invention
The present disclosure relates to a linear actuator for height adjustable columns.
2. Description of Related Art
Linear actuators are used in several different kinds of arrangements. Common for most linear actuators are that a rotational movement of a driving device is transformed to a linear movement of the parts of the linear actuator. One field of application of a linear actuator is in height adjustable columns for height adjustable furniture.
A common kind of linear actuator used in a leg device for furniture is disclosed in WO0071001. The leg device comprises three telescopically arranged tubes, and, inside the tube arrangement, three shafts and a driving device. The first shaft is coupled to the outgoing shaft of the driving device and attached to the inner tube. The first shaft has an external thread in threaded connection with an internal thread on the second shaft. The second shaft also has an external thread in threaded connection with an internal thread on the third shaft. The third shaft is attached to the outer tube. When the driving device rotates, the first shaft rotates and moves longitudinally relative to the second shaft. When an end position in the thread connection between the first and the second shaft is reached the rotation of the first shaft relative to the second shaft is locked so that the second shaft starts to rotate. The second shaft then moves longitudinally relative to the third shaft until the leg device is fully elongated or fully contracted.
The linear actuator in this leg device is rather complicated and a complicated arrangement is also expensive to manufacture.
Consequently, there is a need for a more cost-effective and simpler construction of a linear actuator for height adjustable columns.